High-pressure liquid oxygen converter



Dec. 4, 1951 w. A. WILDHACK HIGH-PRESSURE LIQUID OXYGEN CONVERTER FiledAug. 9 1946 00 William A. Wi'ldhock Patented Dec. 4, 1951 UNITED STATESPATENT OFFICE HIGH-PRESSURE LIQUID OXYGEN CONVERTER (Granted under theact of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) Thisinvention relates to liquid oxygen converters and more especially toapparatus for charging high-pressure oxygen cylinders from a source ofliquid oxygen.

The object of the present invention is to de-= vise apparatus whereby tocharge high-pressure oxygen cylinders from a liquid oxygen source in amost expeditious and efficient manner.

Another object is to devise apparatus whereby liquid oxygen and otherliquid fuel can be delivered at high pressures to evaporators orcombustion chambers in jet motors, rockets and the like.

Another object is to include in an apparatus for charging high-pressureoxygen cylinders, a container, a conduit with a control valve betweenthe bottom of said container and the source of liquid oxygen. a pressurebuild-up coil connected between the top and bottom of said container anda warming coil connected to the bottom of said container for delivery ofgaseous oxygen at high pressure to one or more oxygen cylinders, saidcoils being exposed to the atmosphere and of suitable length andcapacity to permit sufficient absorption of heat at the desired rate topermit rapid and eificient operation.

Another object is to construct a self-contained liquid oxygen converterapparatus, comprising an insulated container tapped at the top andbottom, a pressure build-up coil between said taps. a pressure-closingvalve in said coil, an evaporator coil connected to the lower tap, saidcoils being spiralled about and suitably spaced from each other and fromthe container for maximum absorption of atmospheric heat, and a flowcontrol means at the end of said evaporator coil.

Another object in this construction is to devise a liquid oxygenconverter which will take liquid oxygen and start charging high-pressureoxygen cylinders at 1800 pounds per square inch within a few minutesafter filling the converter, and in which the charging may beinterrupted at any time and the apparatus allowed to sit idle forseveral hours before any loss occurs from relief of excess pressure.

These objects are accomplished by making use of non-equilibriumconditions of density in a pressure build-up circuit, wherein thegravitational or accelerational pressure due to liquid in the descendingpart of the circuit forces gas formed by evaporation of the liquid in anevaporator to rise in the ascending part of the circuit and to becompressed in a space above the liquid thus increasing the pressurethroughout the enease of maintaining temperature gradients in liquidoxygen, due to its rapid change of density with temperature, to obtainvery high pressures quickly without warming the mass of liquid to bedelivered. The gas compressed over the liquid by reason of gravitationalcirculation in the pressure build-up circuit partially condenses on thesurface of the liquid forming a hot layer with a surface temperaturecorresponding to a vapor pressure approximately equal to the actualpressure in the system.

This mode of operation is the same as described in my copendingapplications Serial No. 647,411, filed February 13, 1946, on LiquidOxygen Converters and serial Number 645,692, filed February 5, 1946 onLiquid Oxygen Converters.

Other and more specific objects will appear in the following detaileddescription of one form of the apparatus which was built in accordancewith this invention, having reference to the accompanying drawings inwhich:

Fig. 1 illustrates diagrammatically the combination of parts of thepresent embodiment of the apparatus exemplifying one preferred form ofthe invention; and

Fig. 2 shows one specific application of the present invention used inconnection with rockets or the like.

Referring to Fig. l, the container is shown at l, and has upper andlower taps 2 and 3 respectively, the lower tap being connected to asupply conduit 4 having a shut-off valve 5 of suitable design thereinfor purposes of filling the container preparatory to charging the oxygencylinders (not shown).

The container I used in one form of this converter was adapted from oneof the wire wound aircraft oxygen cylinders used in naval aircraft,having a capacity of about 500 cu. in., mounted in a in. plywood box 6about 14" x 14" x 30" with opacified silica aerogel insulation packing1.

With the pressure build-up coils 8 and the evaporator coil 9 spacedlywound around this box, the overall diameter of the entire apparatus wasabout 23 in. and the overall height about 44 in. The total weight wasabout 111 lbs.

The cylinder was modified by removing the valve and welding in a plugwhich was tapped for A;-inch pipe at 2, and by welding in a -inch pipenipple at the opposite end at 3. This container I was suspended in a boxas shown in Fig. 1 and had a stainless steel tube It] about 30 incheslong of iQ-inch inner diameter (0.009

tire system. Advantage is taken of the relative inch wall of thickness)at each end leading to the outside of the box. The tubes were coiledinside the box, and in addition the bottom tube was bent so that aliquid trap was formed at Ii close to the container. The box was closedtightly and the space between box and container was filled with silicaaerogel I for insulation.

Outside the box the tubes N from the container terminated inpipe-crosses l2 and It to which were soldered flanges for fastening themto the box. One of the outlets l4 of the lower pipe-cross l3 wasconnected to the set of pressure build-up coils 8, one l5 to theevaporator coil 9, and one IE to the flller connection 4. One outlet llof the upper pipe-cross l2 was connected to a pressure gage l8 and asafety blowout plug l9, while two outlets and 2| were connected tomanually operated high pressure line valves 22 and 23, one of which 22was in series with the pressure build-up coils 8 and a pressure closingvalve 24, while the other 23 was for relieving to the atmosphere the gaswhich is internally developed during filling of the container i.

In some models, it may be preferable to use a vacuum space forinsulation instead of the aerogel packing I. No difficulty should beencountered in fabricating such a vessel, since it will entail only theaddition of a relatively light container surrounding the pressure tank.The surfaces of both containers next to the vacuum will requirepolishing or plating to give high reflectance for insulating efllciency.

The evaporative capacity of the pressure buildup circuit, consisting offour parallel branches each of 36 feet length and made of inch coppertubing, was about 300 liters per minute (standard temperature andpressure) as determined by the flow that could be drawn off the gasphase while the pressure was maintained at 1800 pounds per square inch.The temperature of the gas delivered at the top of the pressure build-upcircuit was as low as --50 0., however.

The time required to build the pressure up to 1800 pounds per squareinch when the container is full is about one minute. This representsevaporation of suflicient gas to fill the tubes (40% of the volume ofthe whole apparatus), as well as any void in the internal container leftby the evaporation of that gas, to a pressure of 1800 pounds per squareinch.

The pressure closing valve 24 was made by enlarging the valve port of anordinary single stage high-pressure pressure reducer and installing itin series with the pressure build-up coils and the manual valve 22. Itsoperation is such that the valve remains open, allowing circulation,until a certain pressure (depending upon the adjustable spring pressureon the diaphragm of the pressure reducer) is reached, when it closes.stopping the circulation. Since this rate of flow should be large andthe driving force is only the diflerential pressure due to differingdensity of gas and liquid columns, the resistance to flow in thepressure build-up circuit must be held to a minimum. In designing orselecting the pressure closing valve, these requirements shouldtherefore be kept in mind.

The evaporation coil 9 was composed of about 200 feet of 1%" O. D.copper tubing (0.035 inch wall) coiled around the box 6 starting at thelower pipe-cross l3, spiralling upward to the top, and then back down ina'larger diameter spiral. The space between the two spirals wasmaintained at about one inch by wooden spacers at 4 the four corners ofthe box. The coil had in series with it at its terminus the flowcontroller 25 and a manually controlled valve 26.

When constructed, the length was limited by the amount of tubingavailable. No limitation is placed on the length by the general design,however, and twice as much evaporative capacity would be desirable. Acoil, of the dimension cited, will evaporate and warm 200 liters permeter of gas normal temperature and pressure to within 20 of ambienttemperature, 300 liters per minute to within about 30, or 400 liters perminute to within 60.

Both the pressure build-up coil and the main delivery coil can equallywell be replaced by other types of heat exchangers, for atmosphericheating, or by other types of heaters, such as electric or flame.Particularly in the case of jet motors of rockets, flame heating of thepressure build-up evaporator which may be a coil, a jacket or manifoldof tubes in or surrounding the combustion chamber, is desirable toincrease the rate of delivery.

The diagrammatic showing in Fig. 2 is illustrative of one adaptation ofthe invention in which flame heating is used, in connection with a jetmotor. The evaporator coil 2'! corresponding to coils 8 of Fig. 1 may bein contact with or incorporated as a jacket in the wall of thecombustion chamber 28 of the Jet motor and has inlet connection to theoxygen container through conduit 46 and trap 41. The outlet 29 from thiscoil is connected to the upper portions of the oxygen and fuelcontainers 30 and 3| through pressure closing valves 32 and 33respectively, thus providing the necessary high pressure for supplyingthe liquid oxygen and fuel to their respective high pressure burner jets34 and 35 through the pressure opening valves 36 and 31 and controllers38 and 39 respectively. The oxygen and fuel are withdrawn from thebottoms of their containers by conduits 44 and 45 which are providedwith container filler connections 42 and 43 having cut-01f valves 40 and4i therein respectively. Traps 48 and 49 are also provided as indicated.For jet use a warming. delivery coil corresponding to 9 of Fig. l isunnecessary, the discharge being directly into the combustion chamber 28of the motor.

The flow controller 25 was devised to regulate the delivery flow, and tolimit it to a value within the evaporating capacity of the coil 9. Theflow controller 25 was constructed by placing a restriction upstream toand in series with a line valve of the diaphragm type, wherein thepacking is replaced by a diaphragm which flexes against the valve rod toclose the valve. The line valve was connected so that direction of flowwas such that the fluid would enter the valve into the space directlybeneath the diaphragm, that is, opposite to the normal direction. Theupper valve stem was removed from the valve and a tube, connected to thedelivery line upstream of the restriction, was connected to the openingleft by the upper valve stem, so that the upstream pressure would act todepress the diaphragm and close the valve. The valve spring and thedownstream pressure both tend to hold the valve open, so that the netpressure differential across the restriction operating on the diaphragmwill close the valve when it becomes great enough to overcome the springaction. The pressure in the valve below the diaphragm is thus maintainedat a constant diilferential below that in the supply line, therebymaintaining the same differential across the restriction. The flowthrough the device is then that which will pass the restriction on theset difierential determined by the diaphragm and Spring characteristics.The flow, while not constant at varying pressure because of thecorresponding variation in density, is quite constant for a fixeddelivery pressure.

Inasmuch as one of the main applications of a flow controller is toprevent delivery of too cold 9. gas, or of liquid, a thermallyresponsive valve can be used. For constant rate of delivery thecontrolled pressure acting across a fixed restriction in the liquiddelivery line is the simplest arrangement.

Operation During operation, the outlet of the converter beyond valve 26is connected with a bank of cylinders to be filled. The chargingpressure, at the cylinder manifold, is indicated by a large gagesuitably placed. The converter pressure is indicated by the small gage18 mounted near the top of the converter.

In filling, the liquid supply is connected to the filler connection 4,the pressure build-up control valve 22 closed, the relief valve 23opened, and the liquid is forced in under pressure. When full(determined by weighing or, more simply, by the issuance of liquid fromthe relief valve exit) the relief valve is closed and the fillerdisconnected.

Opening of the manual valve 22 in the pressure build-up circuit thenallows circulation. to proceed in the pressure build-up coils 8. Liquidflows out the bottom tap and vaporizes in the coils by absorbingatmospheric heat, the resulting gas going back into the containerthrough the top tap 2. Because of the active evaporation in coils 8, thelevel of the liquid in these coils is lower than the liquid level incontainer I, so that a hydrostatic pressure difierential is available tomaintain the circulation. Some of the evaporated gas goes to developingpressure over the liquid and some recondenses in the liquid to form awarmer layer at the surface. This process continues until suflicientpressure is developed to close the pressure closing valve 24, or untilthe manual valve 22 is closed.

With pressure in the container I, and the delivery valve 26 open, liquidis forced out into the evaporator coil 9 where is vaporizes byatmospheric heat.

Modifications and improvements in design may be made without departingfrom the spirit and scope of this invention, as defined in the appendedclaims.

The invention described herein may be manufactured and used by or forthe Government of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefor.

What is claimed is:

' 1. A high pressure liquid oxygen converter comprising an insulatedcontainer having upper and lower connections including a liquid trap insaid lower connection, one or more pressure build-up coils exposed tothe atmosphere, connected in parallel between said upper and lowerconnections, and having a pressure closing. valve and a control valve inseries near the upper connection, said coils extending downwardly to alevel below the bottom of said container, and a warming delivery coilexposed to the atmosphere connected to the lower connection and having apressure responsive flow control valve and a 6 manual shut-off valve inseries at its outer end for delivery of high pressure oxygen.

2. A high pressure liquid oxygen converter comprising an insulatedcontainer having upper and lower connections including a liquid trap insaid lower connection, one or more pressure build-up coils exposed tothe atmosphere, connected in parallel between said upper and lowerconnections, and having a pressure closing valve and, a control valve inseries near the upper connection, said coils extending downwardly to alevel below the bottom of said container, and a warming delivery coilexposed at the atmosphere open to the liquid phase in said container,and having a pressure responsive flow control valve and a manualshut-ofl valve in series at its outer end for delivery of highpressureoxygen.

3. A high pressure liquid oxygen converter comprising an insulatedcontainer having upper and lower connections including a liquid trap insaid lower connection, one or more pressure build-up coils exposed tothe atmosphere, con-- nected in parallel between said upper and lowerconnections, and having a pressure closing valve and a control valve inseries near the upper connection, said coils extending downwardly to alevel below the bottom of said container, a warming delivery coilexposed to the atmosphere connected to the lower connection and havingan automatic flow control valve and a manual shutoif valve in series atits outer end for delivery of high pressure oxygen.

4. A high pressure liquid oxygen converter comprising an insulatedcontainer having upper and lower connections including a liquid trap insaid lower connection, one or more pressure buildup coils exposed to theatmosphere, connected in parallel between said upper and lowerconnections, and having a pressure closing valve and a control valve inseries near the upper connection, said coils extending downwardly to alevel below the bottom of said container, a warming delivery coilexposed to the atmosphere open to the liquid phase in said container,and having an automatic flow control valve and a manual shut-off valvein series at its outer end for delivery of high.

pressure oxygen.

5. A liquid oxygen container having upper and lower connectionsincluding a liquid trap in said lower connection, atmospheric heatabsorption means connected between said upper and lower connectionslocated at least partially below the level of the bottom of saidcontainer for vaporizing a portion of the contents and causing acirculation therethrough automatically, a pressure closing valve nearthe upper connection for stopping said circulation when a predeterminedpressure is reached, and delivery means exposed to the atmosphere opento the liquid phase in said container for delivering said oxygen at saidpredetermined pressure, said delivery means being provided with anautomatic control valve and a manual control valve.

6. A liquid oxygen container having upper and lower connectionsincluding a liquid trap in said lower connection, atmospheric heatabsorption means connected between said upper and lower connectionslocated at least partially below the level of the bottom of saidcontainer for vaporizing a portion of the contents and causing acirculation therethrough automatically, a pressure closing valve nearthe upper connection for stopping said circulation when a predeterminedpressure is reached, and delivery means exposed to the atmosphereconnected to the lower end of said container for delivering said oxygenat said predetermined pressure, said delivery means being provided withan automatic control valve and a manual control valve.

7. A main liquid container having upper and lower connections, a liquidtrap in said lower connection, heat absorption means connected betweensaid upper and lower connections located at least partially below thelevel of the bottom of said container for vaporizing a portion of thecontents thereof and causing a circulation therethrough automatically, apressure closing valve for stopping said circulation when apredetermined pressure is reached, and delivery means open to the liquidphase in said container for delivering said liquid at said predeterminedpressure, said delivery means including an automatic control valve.

8. The apparatus of claim 7 with at least one additional container forholding a liquid, a conduit between the gas phase region of saidadditional container and the upper connection of said main container, asecond pressure closing valve in said conduit, and delivery means opento the liquid phase in said additional container for delivery of liquidtherein at a predetermined pressu e as fixed by said second pressureclosing valve.

a 8 9. The apparatus as defined in claim 8 including additionally amixing chamber ior combining the output of said container deliverymeans.

10. The apparatus as defined in claim 8, including additionally anautomatic pressure control valve in each of said delivery means.

WILLIAM A. WILDHACK.

REFERENCES CITED The following references are of record in the tile ofthis patent:

UNITED STATES PATENTS Number Name Date 1,866,514 Heylandt July 5, 19322,180,090 Mesinger Nov. 14, 1939 2,226,810 Ensign et al. Dec. 31, 19402,363,960 Hansen Nov. 28, 1944 2,368,680 Riise Feb. 6, 1945 2,397,657Goddard Apr. 2, 1946 2,408,111 Traux et al. Sept. 24, 1946 2,464,835Thayer Mar. 22, 1949 FOREIGN PATENTS Number Country Date 378,895 ItalyFeb. 27, 1940 OTHER REFERENCES Astronautics, N0. 34 June 1936, pp. 8-13.

